Chloropolysilanes have conventionally been produced by chlorination of silicon materials which comprises passing hot chlorine gas through particles of a silicon alloy material such as calcium-silicon, magnesium-silicon, ferrosilicon, etc. or metallic silicon.
However, when chloropolysilanes are prepared by chlorination of the above-mentioned silicide materials, solid by-products such as calcium chloride, magnesium chloride, iron chlorides, etc. are produced. This is undesirable and a commercial process for producing chloropolysilanes without producing solid wastes is desired.
In the case of the reaction of silicon particles and chlorine, no solid waste is produced, but the yield of chloropolysilanes is very low and may be less than 1 mole% on the basis of gram atomic weight of silicon.
Also, in the conventional process, mainly chlorosilanes SiCl.sub.4 is produced, and chloropolysilanes Si.sub.2 Cl.sub.6, Si.sub.3 Cl.sub.8, etc. are produced only in small amounts as by-products of SiCl.sub.4.
We studied the chlorination of silicon particles for production of chloropolysilanes in search of methods in which the yield thereof is high and have found that formation of chloropolysilanes is promoted while the formation of SiH.sub.4 is depressed by addition of copper or some copper compounds as catalysts to silicon particles in chlorination.